Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Biology Hon. Ch. 15
Populations
| Population | |
|---|---|
| Population | all the individuals of a species that live in one place at one time -people in Omaha -people in the world -ducks in Eastern Nebraska -deer in a forest |
| Devil's Hole Pupfish | Death Valley, isolate area, only pop. of this fish in the entire world |
| 3 key features of pop. | a) pop. size (small pop. more in danger) b) pop. density (number of ind. in a certain area, a ratio) c) dispersion (the way the ind. are arranged) |
| pop. model | a hypothetical pop. that has the key caracteristics of a real pop. |
| carrying capacity | the pop. size that an environment can support |
| *R-strategists* | a) pop. that grow very fast (explosions) b)some insects, annual plants, bacteria c) young mature and grow quickly |
| *K-strategists* | a) whales, rhinos, redwood trees b) slow pop. growth, live in environments that are stable and predictiable |
| humans | have many traits of k-strategists BUT have changed the environment to greatly increase "carrying capacity" |
| Hardy-Weinberg Principle | (1908) a) pop. don't change unless evolutionary forces act upon them b) true only for large pop. in which ind. mate randomly and the forces that change the proportions of alleles are not acting c) uses math to predict the frequency of each genotype in |
| 5 forces causing evolution in pop. (1-3) | 1.MUTAION-changing of alleles, doesn't happen often 2. MIGRATION-movement of ind. from 1 pop. to another, creates a gene flow (mixing of new genes and alleles) 3. NONRANDOM MATING-when ind. mate w/ others of their own geneo. (inbreed-mating w/ relatives) |
| 5 forces causing evolution in pop. (cont: 4-5) | 4. GENETIC DRIFT-small pop, chance event causes the freq. of alleles to change, this has affected humans-----we used to live in small, isolated groups or tribes 5. NATURAL SELECT.-causes deviations from Hardy-Wein by directly changing the freq. of alleles |
| Natural selection | reduces the frequency of a harmful recessive allele slowly because very few ind. are homozygous recessive and express the trait |
| genetic polymorphism | when a gene in a pop. has more than one allele appearing at a significant frequency |
| polygenic trait | a characteristic influenced by severaL genes (human height), often results in a normal distribution |
| directional selection | when selection acts to eleminate one extreme from a range of phenotypes, the genes promoting this extreme become less common |
| stabalizing selection | when selection acts to eliminate extremes at both ends of a range of phenotypes, increases the number of ind. that are similar |
| disruptive selection | when selection acts to eliminate rather than favor the "average", the pop. will have a larger number of ind. at the 2 extremes |
Created by:
kecordell
Popular Biology sets